Electrical precipitator



Nov. 22, 1927.

W. A. SCHMIDT ELECTRICAL PRECIPITATOR 2 Sheets-Sheet 1 Filed Sept. 9. 1925 INVENTR Waler BYQL/ fj Nov. 22, 1927.

w. A. SCHMIDT ELECTRICAL PREIPITATOF Filed sept. 9. 1925 2 Sheets-Sheet 2 Fay. 'a

IN VEN TOR Wa Zier/7.l Scie/nidi B YaM// A T NE Y Patented Nov. 22, 1927.

UNITED sTATEs PATENT OFFICE.

WALTER A. SCHMIDT, OF LOS ANGELES, CALIFORNIA, ASSIGNOR T0 INTERNATIONAL PRECIPITATION COMPANY, OF LOS ANGELES, CALIFORNIA,

CALIFORNIA.

ELECTRICAL PRECIPITATOR. l

i Application led September 9, 1925. Serial No. 55,383.

This invention relates to apparatus for separation of suspended particles from gases by electrical action andpparticularly to the form of such apparatus in which the gases containing the particles are passed between electro'des maintained at a high potential dierence and so constructed as to produce an electrical discharge from certain of said electrodes, resulting in charging of the suspended particles and the deposition of charged particles on the electrodes and particularly on the electrodes opposing the 4discharge electrodes.

The main object of the present invention is to provide in an electrical precipitator of this character, means for increasing the eiciency and capacity of the vprecipitator by increasing the amount of electrical discharge therein, Another object of the invention is to provide for distributing the electrical discharge more effectively throughout the body of gas being treated so as to result in a more etiicient precipitation. In electrical precipitators there is a tendency for concentration of the electrical discharge at certain portions of the electrodes leading to certain disadvantageous results. By reason of such concentration of the electrical discharge in such portions or' the electrodes there is liable to be a large portion of the gas being treated which is not subjected to the action of such electrical discharge and consequently such portions of the gas /may Y pass through the electrical preeipitator withspace between the electrodes sufliciently longv gas will be sub.

. jected to electrical out being subjected effectively tothe electrical precipitating-action. In order to ensure contact 'of all portions of the gas with the electrical discharge it has generally been necessary to make the gas velocity extremely slow or to make the conduit or gas treating to ensure that all of the action at some time 'in its passage through such space. Furthermore, by electrical discharge there is liable to bebreaking 'down of the dielectric resistance of the gas tol such an extent as to cause arcing orv disruptive scharge which seriously decreases the eiciency reason of such concentration of of the treater by limit- A CORPORATION OF ing the potential difference which may be maintained between the'electrodes, and by otherwise interfering with the operation of the precipitator,

It has been found that by making the socalled collecting electrodes of semi-conducting or high resistance material so as to interpose a considerable resistance to the passage of current, concentration of the elec-l trical discharge at any one portion or a relatively limited number of portions of the collecting electrodes may be prevented. vI have found,` however, that in connection with a collecting electrode of this character there is a tendency to diminution` of electrical dis charge due to the spreading out of the electrical field, and I have found that'in order to realize the fullbeneit ofthe reater uniformity of electrical eld it is a vantageous to provide a 'discharge electrode adapted to facilitate a more orl less uniform and copious discharge from all portionsthereof at a potential difference below the critical po' tential difference orso-called arcing volt-age between the electrodes. For this purpose I may coat orl surround the discharge electrodes with a material which facilitates the electrical discharge, for example a porous dielectric, which by reason of its facilitating ionization within the pores of such material tends to produce emanation of ions moreor less uniformlyfrom all parts ,of the Isurface thereof. The provision of a discharge electro'de provided with the means as above described. for facilitating., electrical discharge is also of advantage in connection with ametallic or highly conducting collecting electrode.

The accompanyin bodiments of my invention and referring thereto: .Y Fig. 1 is' a vertical transverse section-of one form of my invention.

Fig. 2 is asection on line 2-2 in Filg. 1. Fig. 3 isa section on line 3-3 in ig. 2. Fig. 4 is a' horizontal section of a discharge electrode on/line 4--4 in Fig. 1.

Fig. 5 is a vertical section `of a tubular 'or Aso-'called pipe treater embodying` my invention.

drawingsillustrate ein- Fig. 6 is a horizon-tal section through the tubular treater chamber shown in Fig. 5.

Figs. 7 and 8 are partial vertical sections of modified forms of my invention.

Referring to Figs. 1 to 3 the embodiment of my invention shown therein comprises a casing or conduit 1 having inlet 2 and outlet 3 for the gas to be treated and provided with any desired number of vertical partition walls 4 subdividing the interior of said conduit into a plurality of passages. The walls ofthe fiue 1 and the partition 4 constitute the collecting or so-called passive electrodes and may consist of any suitable semiconducting or high resistance material presenting sufficient conductivity for carrying the precipitating current but presenting sufficiently high resistance to substantially prevent r largely reduce excessive 'concentration of the precipitating current at a point or points of said electrodes. For this purpose said electrode members 1 and 4 may consist of re-enforced concrete or similar material consisting for example of concrete Walls of Portland cement and suitable aggregate and having vertical re-enforcing bars or rods 5 which are arranged in spaced parallelism, for example, vertically and are connected together and to ground by wires or conductors 6. Suitable means such as hopper 7 may be provided below the fiue 1 for receiving the material precipitated upon the. f collecting electrodes and removed therefrom by the action of gravity or in any other suitable manner.

Within the flue space between the walls 1 and the partition means 4 are provided discharge electrodes 8 consisting for example of ywires, rods, or other conductors so constructed as to facilitate electrical discharge therefrom, said wires or conductors 8 bemg suspended from a supporting frame 10 which is mounted on insulators 11 in the other hydraulic binder or with small quantities of bitumen, rosin, or other binder which may be softened by the action of heat. In either case the amount of binder used is sufficiently small as to not impair'seriously the porosity or discontinuity of the material. I prefer to arrange the discharge electrodes in parallelism to the re-inforcements 5 in the collecting electrodes and opposite the spaces between said re-enforcements, so as to equalize the electrical field intensity throughout the surface of the collecting electrode, as set forth in patent to E. Anderson, No. 1,541,67 7 dated June 9, 1925.

The operation is as follows:

A high potential difference preferably unidirectional is applied to the electrodes by connecting the high tension systefn carrying the discharge electrodes 8, through a wire 12 to any suitable source of vhigh tension rectified alternating current, for example in the manner set forth in the U. S. patent to F. G. Cottrell, N o. 895,729, dated August 1l, 1908. 'lhus a strong electric field is produced between the electrode 8 and the opposing electrode with the result that electrical discharge takes place mainly from the electrode 8 on account of the relatively limited cross-section and correspondingly sharp curvature and also on account, of the fact of the coating 9 facilitating such discharge.

This coating has a further effect of distribut-l ing the discharge more or less over the entire surface vof the collecting electrode so as to produce a. discharge or ionization which is presented to all parts of the gas passing between the electrodes. As a result of the uniform distribution of electrical discharge, corona, or ionization throughout the body of gas passing between the electrodes a more rapid and complete electrical charge of the suspended particles in the gas is secured with 7resulting rapid and complete electrical pre-.l

cipitation of the suspended particles, such precipitation taking place by translation of the electrical particlesl under action of the electrical field toward the collecting electrodes, it being understood that the particles will be electrically charged in the same sense as the discharge electrodes and will therefore be forced by the action of the electrical field away from the discharge electrode and toward the collecting electrode. By reason of the semi-conducting nature of the collecting electrode it is possible to produce such eX- tended or distributed discharge from all or y a large part of the surface of the discharge electrodes without danger of undue concentration of electrical discharge at any part of the collecting electrodes such as would otherwise be liable to lead to a break-down of the dielectric resistance of the gases. The potential difference between the electrodes may therefore be maintained sufiiciently high to ensure such extended or distributed discharge from the discharge electrodes without causing disruptive discharge to any serip ous extent. By reason of the large amount of electrical discharge produced as above described and its more or less unlform distribution in contact with the gas passing between the electrodes, a correspondingly large amount of gas can be treated effectively in a precipitator of relatively limited size. The material deposited on the collecting electrode mounted on suitable insulating means and being coated with or surrounded by discontinuous or porous dielectric indicated at as above described. The operation of this form of my invention is the same as that of the plate type precipitator shown in Figs. 1 to 3 and it will be understood in practice that any suitable number of vertical flues or pipes may be connected in parallel arn rangement in the usual manner of the multiple pipe electrical precipitators.

In place of using a. porous dielectric any other means may be provided for facilitating discharge from the discharge electrodes in connection with the semi-conducting collecting electrodle construction for preventing concentration of the discharge in any part thereof. For example the discharge electrode may be coated withiradio-active material such as uranium ore, or radium ore, or products thereof. Or, as shown in Fig. 7 the discharge electrode may. comprise al-f ternately arranged dielectric or non-condueting members 18, such as discs or plates of mica., 'or asbestos, or like material, and conductor'members 20 formed for example of metal discs or plates, all supported on discharge electrode conductor 21 in such man# ner that the non-conducting elements constitute a discontinuous dielectric at the di-scharge surface tending to facilitate ionization and discharge. Any other means for providing for a discontinuous dielectric at the discharge surface ma be employed provided it is such as to acilitate ionization throughout such discharge surface. The collecting electrode 22 maybe similarvto that shown in Fig. 5.

While I have described my invention as particularly applied in connection with electricgal precipitators having collecting or passive electrodes formed of semi-conducting or high resistance material, it may also be applied in some cases with advantage to precipitators in which the collecting electrodes are of good conducting material such as metal. Such a construction is shown in Fig. 8, the .collecting electrode 23 being shown as a conducting pipe of metal and the discharge electrode being shown as a metallic conductor 24 insulated from the' collecting electrode and provided with a. coating indi,- cated at 25 and constituting a vrous dielectric or discontinuous dielectric 1n the manner above described. v

precipitator, such deposit It will be understood that in the operation of the electrical precipitator such as above described there will be lin general some depolsition of electrically precipitated material on the surface of the discharge electrode, although the major portion of the electrical precipitation will take place on the collecting or passive elect-rode. In so far as there is deposition of non-conducting material on thelischarge electrode, such deposition, provided it is of porous or discontinuous nature will not interfere with the operation of the inventio-n as it forms substantially an extension of the porous or discontinuous dielectric surface of the discharge electrode, it being understood that such deposited material will not in general be permitted to accumulate to a suilicient thickness ,to interfere with the iiow of gas through the precipitator, or otherwise interfere with the o ration of the Ibeing removed by any suitable' means such as rapping, scraping, or brushing, or by the action of gravity alone, in the usual manner in electrical precipit-ators of this character. In each of the above described embodiments of my invention the discharge electrodes' are shown as of relatively limited area and relatively sharp curvature and the collecting electrodes as presenting flat surfaces or surfaces which are concave toward the electrical field, the effect being in either case to facilitate discharge from the discharge electrodes and to prevent or reduce discharge from the collecting electrodes, and such. a construction of the electrodes tending to limit the discharge as far as possible to the discharge electrodes is a preliminary conditionl of the successful carrying out of my invention which provides for increasing and electrical precipitator having the electrodes of the character described.

I claim:

1. An apparatus for vseparating suspended particles from gases by electrical action, com-A prising a collecting electrode having high resistance, and a discharge electrode insulated from the collecting electrode and consisting of conducting material covered with material facilitating uniform electrical discharge and means for maintaining said discharge and collecting electrodes at high potential di'erence.

2.- An a paratus for separating suspended' material om gases comprising a discharge electrode of conducting material and of relatively-limited area. surrounded with a porous dielectric adapted to facilitate ionization and electrical discharge throughout' its said discharge electrode of relative tended area and presenting high resistance throughout its area, so as to prevent consurface, and a collecting electrode opposing yv excentration of electrical discharge at any part..

of its surface.

3. An apparatus for separat-ing suspended particles from gases, comprising grounded collecting el-ectrodes and discharge electrodes insulated from the` collecting electrodes and means for maintaining said electrodes at high potential difference, each collecting electrode comprising concrete members of extended area, and metallic re-enf-orcements ext-ending in parallelism and in spaced relation Within said concrete member and connected to ground, and the discharge electrodes consisting of metallic members of relatively limited area, extending parallel to the re-enforcements iu the collecting electrodes and opposite the spaces between said re-enforcements, and the discharge electrodes being coated with material facilitating disprising a discharge electrode of relativelylimited area, and a collecting electrode of relatively extended area opposing said discharge electrode, said discharge electrode having its discharge surface provided with a porous dielectric adapted tofacilitate uniform discharge therefrom.`

In testimony whereof I have hereunto subscribed my name this 28th day of August,

v WALTER A. SCHMIDT. l 

